Combustion system



Filed March 26, 1957 United States Patent 6 COMBUSTION SYSTEM GabrielBrola, Bourg la Reine, France, assignor to Genrale Thermique-ProcedesBrola, Le Pre Saint-Gervais,

rance Application March 26, 1957, Serial No. 648,704

Claims priority, application France March 29, 1956 '6 Claims. (Cl.158-77) In the steady-state operation of a burner, the flame propagationvelocity must equal the rate of feed of the combustible mixture to theburner. Whenever it is desired to increase the combustion rate,therefore, it is necessary simultaneously to increase the flamevelocity. The present invention provide a combustion system whereby sucha result is conveniently accomplished. In the improved combustion systemmeans are provided for creating within the ignited mixture of fuel andair, vortices that act to return said mixture rearwards, or in otherwords to recycle the flame.

Another object of the invention is to provide an improved burner forliquid or gaseous fuels based on the principle just set forth. Theimproved burner is principally characterized in that it includesmeans'for creating vortices within the burning mixture to recycle theflame.

In a preferred embodiment of the invention, the burner may comprise arotary spray-nozzle consisting of a pair of concentric, axially-spacedrotary cup elements defin ing between them an annular space for theintake of primary air, the foremost or upstream cup element being formedwith a central fuel intake aperture and the rearward or downstream cupelement being formed or provided at its terminal end with fins arrangedadjacent a fixed wall surface or shoulder so as to define a secondaryair passage so arranged that the secondary air will, on contacting themixture of fuel and primary air, generate an annular vortex generallycoaxial with the cup elements and directed rearward.

' In cases where the burner is arranged within a furnace tube, thedownstream cup element is preferably provided along its edge withbafiles adapted to channelize part of the secondary air into the furnacetube. The baffles are rotatable with the cup element and will impart acircular sweep movement to the deflected air stream so that it willsweep past the inner wall surface of the furnace tube thereby preventingformation of carbona- .iceous deposits.

In accordance with a further feature of this invention an electricalresistance for use on starting the burner is arranged in a groove formedaround the combustion chamber and is cooled by an air stream whichsimultaneously serve to prevent formation of uncombusted deposits.

Further according to the invention the rate of supply of the liquid orgaseous fuel is controlled by a needle valve or the like associatedwitha rotary valve seat, an arrangement which will act to eliminateimpurities tending to clog the fuel flow while at the same timeproviding for accurate and uniform flow regulation without requiring anypreliminary fuel filtering step.

The above and further objects, features and advantages of the inventionwill appear clearly from the ensuing description made with reference tothe accompanying drawing wherein:

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Fig. 1 is an axial sectional view of a preferred embodiment of a burneraccording to the invention;

Fig. 2 is a larger-scale sectional view of the spraynozzle used in theembodiment of Fig. 1; and

Fig. 3 is a side view of a detail.

Referring to Fig. 1, an electric motor 1 is shown as driving a shaft 2.The motor 1 is surrounded by a casing 3 having formed in it an aperture4 which is adjustable by means of a valve 5. The shaft 2 directly drivesa fan 6 operating within a casing shell 7 secured with screws to themotor casing 3. The air drawn in through the aperture 4 cools the motorwindings then flows through the fan 6 and is discharged towards theoutlet after flowing through a set of director vanes 8 secured within acasing shell 7a, screwed to the casing shell 7.

An air distributor 9 secured to the casing shell 7a supports vanes orbaffles 10 for distributing the air supplied to it from the fan.

The drive shaft 2 inaddition to driving the fan simultaneously drivesthe rotor 23 of a vane type fuel feed pump. The fuel from the pump isdischarged by way of a duct 24 past a flow controlling or regulatingmeans 25. The body 27 of the fuel feed pump is secured to the casing 3.

The fuel is delivered (by means not appearing in the drawing) from theregulating means 25 into an annular space 28 surrounding the needlevalve 29. The needle valve cooperates with a rotatable valve seat 30formed at the end of, and rotatable with, the drive shaft 2. The fuelflow controlling assembly is likewise secured to the casing 3. Extendingaxially through the drive shaft 2 is a fuel feed duct 31.

Secured on motor shaft 2 by means of a screw 42 is a rotary spray nozzlewhich comprises a coaxial pair of cup members 43 and 44 assembled bymeans of e.g. three spider arms 45. A check-valve having a ball 40applied against its seat by a spring 41 and positioned olfcenter fromthe burner axis controls the fuel feed from duct 31 into an obliquelyextending duct 39 opening into cup member 43. 'The cup member 44 extendsdownstream from cup member 43 so that it operates in tandem or cascaderelation with it. Formed in the inner wall surface of cup 44 is a groove46 which communicates by way of a set of radially outwardly inclinedports 47 with the outer wall surface of the cup member. Pro- I jectingfrom the outer wall surface of the cup member 44 at the outlets of theports is a flange 48.

Removably mounted within cup member 44 is a ring 49 which serves todetermine the flow rate and angle of the primary airflow passing betweencups 43 and 44.

Attached to the downstream edge of cup 44 are a plurality of deflectorvanes 50. Moreover, a set of radial fins 51 are formed around theperiphery of the edge of the cup member 44 and project at an angle bothto the axis of rotation and to a transverse plane. The fins or vanes 51are positioned opposite to a shoulder 52a projecting from a divergentsection of a combustion chamber 52. Centrally arranged is the rotaryspray nozzle. Between the chamber 52 and cup member 44 an annular space53 is defined for the flow of both secondary and tertiary air.

The combustion chamber is formed at its downstream end with acircumferential groove 17 in which a shielded ignition resistor 18 ispositioned. The groove 17 connects with the annular space 53 by way of aplurality of ducts 20 for the tertiary airflow which serves to cool theresistor. The igniting resistor 18 is retained in its groove 17 andprotected by means of a conical member 54 made from refractory metalsheeting formed with a plurality of holes 55 for discharging thetertiary air into the flame.

The furnace tube 22 made of refractory material extends from the outletof the combustion chamber 52 and is removably connected therewith bymeans of a hinge connection 21. i v

The burner just described operates in the following manner. With themotor stationary the 'ign'iter resistor 18 is energized and, when asuitable temperature has been attained by it the motor 1 is started andthe resistor deenergized. The fan 6 now draws in the necessarycombustion air in an amount controlled byradjustment of valve 5. Thisair cools the motor 1, flows through the fan and is discharged intodistributor 9. 1

This primary air flows past vanes 10 which impart to y it a certain,rotational velocity, then passes around the foremost cup member 43 toatomize the film of fuel which is supplied in the manner hereinafterdescribed in detail and which emerges tangentially from the edges ofthat cup member and has a helical movement, including both an axial anda tangential component, imparted thereto by the primary air. Thesecondary air flowing through annular space 53 is directed towards thefins 51 of the rearward cup member 44. The secondary air flows pastthese fins in a direction which includes a tangential component into thecombustion chamber where it encounters the com bustible mixture ofprimary air and fuel. The secondary air flowing past fins 51'has ahigher velocity than that of the combustible mixture because in additionto the axial movement .of the air there is a tangential component ofmotion .due to the rotation of cup 44. As a result, the secondary air onstriking the combustible mixture deflects the mixture towards the axisand tends to direct it back towards the cup member 43. The fins 51 areso positioned and oriented and the intervening space between theshoulder 52a and cup 44 is so dimensioned, with regard to the rates offlow of the air and fuel, that an annular vortex is generated coaxiallywith the burner axis, as shown by the arrows 56. The effect of thisvortex is to increase the combustion rate and to stabilize the flamefront. The combustion thus proceeds in the combustion chamber; the flamethen has tertiary air fed to it. This tertiary airflow is dischargedfrom the annular space 53 through the openings 20 into the circulargroove 17 and finally issues through ports 55 formed in the conicalsecuring member 54. This tertiary air has a further function in that itlikewise serves to cool the igniting resistor 18 when the fan isoperating. This prevents the temperature of the resistor from exceedinga predetermined limit when subiected to radiation from the flame. Thecombustion continues within the furnace tube 22 and terminates finallyat the outlet of the tube.

To prevent carbonaceous deposits within the furnace tube 22, part of thesecondary air is introduced tangentially into the chamber and isdirected towards the inner wall surface of the furnace tube by theaction ofdefiector baffies secured to the cup member 44. The rotationalmovement of the deflectors causes the air to swirl around the wall ofthe furnace tube thereby to burn up progres sively any deposits whichmay tend to settle thereon; while simultaneously protecting therefractory material by a film of cool air. The number and length of thedeflectors and the rotational velocity are so predetermined as toprovidea desired percentage ratio of this scavenging air to secondary air.

The fuel feed pump driven by motor 1 delivers the fuel into annularspace 28 by way of regulating means 25, and then past needle valve 29into axial duct 31. Since seat 30 of valve 29 is rotated, there is nodanger of clogging, and it is possible to eliminate the usualpreliminary filtering of the fuel. The olfcenter location of check valveball 40 subjects the latter :to celltrifugal force which lifts the balloff its seat and thereby permits the fuel to flow into duct 39 only whenthe shaft 2 is being rotated. Under centrifugal force the fuel suppliedthrough duct 39 is forced to spread over the inner surface of cup 43into a thin film and is tangentially projected to impinge on the primaryair which is delivered around that cup. When the motor is stopped thethin residual fuel .film remaining on the wall of cup 43 flowsdownwardly under gravity on to the outer Wall surface of the cup memberfrom which it drops into the groove 46, in cup member '44. The fuel thenflows by way of ports 47 on .to the inner wall surface of combustionchamber 52 whence it is discharged by way 7 Burners according to theinvention possess a very high combustion efficiency and produce ashort;compact, dense and stable flame. This makes them particularly wellsuited for use in combustion apparatus-having limited furnace capacity.1

WhatI claim is: v

1. In a combustion device; the combination of means defining anelongated combustion chamber having opposed ends with an inlet sectionat one of said ends, a rotatable burner nozzle mounted withinsaid inlet,section with the axis of rotation of said nozzle aligned with thelongitudinal axis of said chamber, means rotating said burner nozzlesaid nozzle including a relatively small diameter cup-like member and aconcentric relatively large diameter cup-like member each having a freeedge at which. the cup-like member opens axially in the direction towardthe other of said ends .of the combustion chamber, said large diametercup-like member extend: ing axially beyond said smalldiameter cup-likemember in said direction toward the other end of the chamber and saidnozzle further having an annular space defined between said largediameter and small diameter cuplike members, means supplying fuel intothe interior of said small diameter cup-like member so that thefuel isspread into a thin film over the inner surface thereof by said nozzle,means producing a flow of primary air through said annular space toatomize said free fuel of said film at the edge of said small diametercup-like member and thereby to form a combustible mixture .of theatomized fuel and primary air, means for igniting said combustiblemixture to produce a flame, said means defining the combustion chamberincluding a member having an annular shoulder adjacent said free edgeofsaid large diameter cup-like member and defining an annular spacetherebetween which opens generally towards the longitudinal axis of thecombustion cham ber to form an'inlet for secondary air, and deflectormeans in said inlet for secondary air directing the latter with atangential component of motion so that the secondary air issuingfrom'said inlet forms spiral vortices which heat back said flame andthereby create a stable vortical combustion zone adjacent said nozzle.

2. In a combustion device; the combination as in claim 1, wherein saiddeflector means are fins projecting from said free edge of the largediameter cup-like-memher and, thus, rotating with said nozzle.

3. In a combustion device; the combination as in claim 2, wherein saidfins are each at an angle with respect to a radial plane passing throughthe axis of rotation of the nozzle.

4. In a combustion device; the combination as in claim 1, wherein saidannular space between the large diameter and small diameter cup-likemembers has frusto-conical inner and outer wall surfaces decreasing indiameter in the direction toward said free edge of the small diametercup-like member so that the flow tgf primary air has a radially inwardlydirected component to cause increased impact between the primary and thefuel which is thrown centrifugally from said free edge of the smalldiameter cup-like member.

5. In a combustion device; the combination as in claim 1, furthercomprising defiector vanes extending from said free edge of the largediameter cup-like member for rotation with the latter, said vanesprojecting across said inlet for the secondary air and being directedgenerally toward said other end of the combustion chamber beyond saidannular shoulder of the member included in the means defining thecombustion chamber so that said vanes axially deflect a portion of thesecondary air entering the chamber at said inlet therefor along theinner wall surface of the chamber extending away from said inlet sectionand cause swirling fiow of the deflected portion of the secondary air toform a cooling, scavenging layer of air against said innerwall surface.

6. In a combustion device; the combination of means defining anelongated combustion chamber having opposed ends with an inlet sectionat one of said ends, a rotatable burner nozzle mounted within said inletsection with the axis of rotation of said nozzle aligned with thelongitudinal axis of said chamber, means rotating said burner nozzle,said nozzle including a relatively small diameter cup-like member and aconcentric relatively large diameter cup-like member each having a freeedge at which the cup-like member opens axially in the direction to wardthe other of said ends of the combustion chamber, said large diametercup-like member extending axially beyond said small diameter cup-likemember in said direction toward the other end of the chamber and saidnozzle further having an annular space defined between said largediameter and small diameter cup-like members, means supplying fuel intothe interior of said small diameter cup-like member so that the fuel isspread into a thin film over the inner surface thereof by centrifugalforce upon rotation of said nozzle, means producing a flow of primaryair through said annular space to atomize the fuel of said film at saidfree edge of said small diameter cup-like member and thereby to form acombustible mixture of the atomized fuel and primary air, said meansdefining the combustion chamber including a member having an annularshoulder adjacent said free edge of said relatively large diametercup-like member and defining an annular space therebetween forming aninlet for secondary air, said means defining the combustion chamberfurther having an annular groove opening into said chamber at a locationbeyond said inlet for secondary air in the direction toward said otherend of the chamber, electrical resistance means in said annular groovefor igniting said combustible mixture to produce a flamedefiector meansin said inlet for directing secondary air flowing through the latter sothat the secondary air beats back said fiame and creates a stablevortical combustion zone adjacent said nozzle, duct means opening intosaid annular groove for supplying a flow of tertiary air through thelatter to said chamber so that said tertiary air cools said resistancemeans during normal operation of the combustion device, said largediameter cup-like member having radial openings therethroughcommunicating with said duct means for the tertiary air flow so that,when rotation of the nozzle is halted, fuel remaining in said smalldiameter cup-like member can drip into said large diameter cup-likememher to pass through the lowermost of said radial openings into saidduct means for collection in said annular groove, whereby saidresistance means can ignite the fuel collected in said annular grooveupon subsequent starting of the combustion device.

References Qited in the file of this patent UNITED STATES PATENTS1,697,279 Klemm Jan. 1, 1929 1,699,488 Klemm Jan. 15, 1929 1,726,640Benniger Sept. 3, 1929 1,935,318 Hawxhurst Nov. 14, 1933 2,005,832Vidalie June 25, 1935 2,200,826 Johnson May 14, 1940 2,680,951 WinterJune 15, 1954

